The present invention relates generally to machine control, and more particularly to grade control in earth-moving operations.
Various types of machines, generally referred to herein as earthmoving machines, have been developed that alter the topology or geography of terrain. For example, scrapers, graders and bulldozers with an attached and moveable cutting blade may be used in various earthmoving applications. During construction site preparation, these machines may be used to level (or apply some predetermined slope, or grade) to the ground prior to construction of a building on the ground. Such earthmoving machines are also useful in road and other construction applications. Of course, there are various uses for scrapers, graders and bulldozers and other earthmoving machines.
Initially, the operation of earthmoving machines was performed by skilled operators in conjunction with a ground crew, for example a crew of grade correctors equipped with surveying instruments to ensure correct grading. This mode of operation continues to be in widespread use today. One disadvantage of this mode of operation is that it is time consuming and labor intensive. Accordingly, there have been various attempts at automating and precisely controlling grading and other operations of earthmoving machines. For example, navigation tools (such as laser systems and satellite based systems) have been employed to help automate these tasks. For example, U.S. Patent Application Publication 2003/0137658 A1 published Jul. 24, 2003, incorporated by reference herein in its entirety, discloses the use of a rotating laser in conjunction with a satellite based navigation system for use in controlling a bulldozer. Using such methods, the position of the bulldozer and the cutting blade can be precisely determined.
One of the constraints of existing systems is that, even though the position of the blade is known with a high degree of accuracy, it is often difficult for an operator of the scraper, grader or bulldozer or other earth-moving machine to determine with sufficient accuracy the position of the blade in relation to a desired grade. Prior attempts to provide indications of the position of the blade relative to the desired grade have typically involved placing a plurality of Light Emitting Diodes (LEDs) in a position viewable by the operator. However, such LED-based systems were typically limited in the range of indication of blade position that they could provide, therefore potentially resulting in inaccurate grading.